Description:

Low-volatility organic compounds (LVOCs) in the gas phase are believed to play a central role in the formation of nucleation-mode particles and secondary organic aerosol, but at present are extremely poorly constrained. The proposed work would provide volatility-resolved measurements of the amount and chemical properties of LVOC emitted from mobile sources, as well as estimates of the effects of modern emission control technology on LVOC emissions.

Objective:

The objective of the proposed work is to improve emission inventories from mobile sources, providing inputs to microphysical/chemical modules important to air quality predictions. Present inventories of LVOCs are limited to total mass, or concentrations of only a few species, with little information about the chemistry or volatility of the total emissions.

Approach:

A novel approach for the measurement and chemical characterization of LVOCs will be demonstrated, using techniques that are currently the basis of aerosol mass spectrometry. LVOCs will be measured in bulk but separated by volatility, allowing for the direct determination of the volatility distributions of such species. This will enable the compilation of emissions profiles made up of groups of organics that span a range in vapor pressures, rather than of individual organic species (the current paradigm for VOC emissions inventories). Such volatility-resolved emissions profiles will be obtained for mobile sources by measuring engine emissions in the laboratory, with LVOC profiles collected as a function of fuel type, load, and emissions-control technology. Particular focus will be placed on emissions from heavy-duty diesel engines, and the effects of state-of-the-art emission-control technologies aimed at reducing emissions of particulate matter, NOx, and hydrocarbons. Additionally, roadside measurements of LVOCs will be made within the context of a multi-instrument field campaign, in order to measure bulk emissions from in-use vehicles.

Expected Results:

The emissions profiles generated from this work will be unique in that all LVOCs will be directly measured, resolved by volatility, and chemically characterized. Thus they will provide the first accurate inputs to microphysical/chemical modules for predicting the formation of nucleation-mode particles and secondary organic aerosol, which are crucial for understanding present and future air quality and assessing risks associated with emissions.

Supplemental Keywords:

Progress and Final Reports:

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.